Mass spectrometry of methyltetrazoles

Abstract

Abstract-The m a s spectra of tetrazole, al1 isomers of mononiethyl-and dimethyltetrazole, several trifluoromethyl substituted tetrazoles, as well as deuterated analogs, were recorded. Loss of N, was the important fragmentation of the molecular ions of tetrazole and 2-niethyl substituted tetrazoles; however, HN2 loss was more important for 1-methyl substituted tetrazoles. The l-methyltetrazoles showed molecular ion peaks while the 2-methyltetrazoles exhibited an unprecedented [M + 11 peak with no molecular ion.NUMEROUS papers have recently appeared on the mass spectral fragmentation of various azoles including pyrroles,l imidazoles2 and pyrazoles? A brief report4 on the metastable transitions of s-triazole has appeared, but no detailed study of substituted triazoles has been reported. A study of the tetrazoles was missing untii the recent work of Fraser and H a g~e ,~ who reported the primary fragmentations of several 1-and 2-methyl-5-aryltetrazoles. They showed that the position of N-methyl substitution of 5-aryltetrazoles could be differentiated by mass spectrometry. With 1-methyl substitution the loss of a fragment of m/e 42 (N3 or CH,N,) was important while loss of N, was only 6 % of the base peak. In contrast, with 2-methyl substitution [M -N,] was the base peak.It is desired to report here a thorough study of the mass spectral fragmentation of tetrazole (1), 1-methyl-(11), 2-methyl-(III), 5-methyl-(IV), 1 ,5-dimethyl-(V), 2,5-dimethyl-(VI), 5-trifluoromethyl-(VII), 1 -methyl-5-trifluoromethyl-(VIII), 2-methyl-5-trifluoromethyitetrazole (IX), and several deuterated analogs (X) to (XIV).For the purposes of discussing the fragmentations observed, the tetrazoles studied fa11 into three structural categories, i.e. 2-methyl substitution, 1-methyl substitution, and those unsubstituted on nitrogen. The cleavages of the molecular ion [MI can be represented schematically for this discussion by a wiggly line bisecting the molecular ion into two fragments with the charge being retained on the portion * National Rescarch Council Postdoctoral Research Associate.

Visual Pigments and Bacteriorhodopsins Formed From Aromatic Retinal Analogs

“…The structures of all intermediates and retinals were ascertained by NMR, UV and MS measurements. The 9-cis *The position of methylation was determined by ELMS according to Forkey and Carpenter (1969). isomers were used for binding studies with bovine opsin whereas the all-trans isomers were used for the formation of bR analogs.…”

Electron impact induced rearrangement of 3,4-disubstituted 1,2,4-oxadiazole-5(4H)-thiones

“…Substituted diazirine ions were also reported as the major fragment ions in the EI fragmentation of substituted tri-and tetrazoles. [18][19][20] Only the spectrum of 6 does not contain ion c but the presence of ion [c…”

Substituent Effects on EI-MS Fragmentation Patterns of 5-Allyloxy-1-aryl-tetrazoles and 4-Allyl-1-aryl-tetrazole-5-ones; Correlation with UV-Induced Fragmentation Channels

“…N 2 elimination was also shown to be the preferential primary fragmentation process during studies conducted by Fischer et al and Shurukhin et al, on 5-(1-acyl-2-dialkylaminovinyl)-1-aryl-1H-tetrazoles and 1-( o -, m -, and p -tolyl)-5-phenyltetrazoles, respectively [ 23 , 24 ]. Nevertheless, although some important features are frequently retained, one important conclusion to withhold is that electron ionization-induced cleavages in this class of compounds are highly dependent upon the nature of the substituents [ 22 , 23 , 25 , 26 ]. In parallel, studies on the photochemistry of some substituted tetrazoles have shown that the preferential structures formed from photocleavage are azides, aziridines and isocyanates, with the nature of the substituents attached to the tetrazole ring strongly influencing the fate of photoreactions, whether due to their chemical nature, the possibility of cross-reactions or conformational impairments [ 16 , 27 , 28 , 29 ].…”